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Message-ID: <bc97a322585926cf357c61ad0dcbf814@codeaurora.org>
Date: Tue, 20 Jul 2021 11:16:13 +0530
From: schowdhu@...eaurora.org
To: Andy Gross <agross@...nel.org>,
Bjorn Andersson <bjorn.andersson@...aro.org>,
Rob Herring <robh+dt@...nel.org>
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>,
Sibi Sankar <sibis@...eaurora.org>,
Rajendra Nayak <rnayak@...eaurora.org>, vkoul@...nel.org
Subject: Re: [PATCH V5 0/4] Add driver support for Data Capture and Compare
Engine(DCC) for SM8150
On 2021-06-30 19:19, Souradeep Chowdhury wrote:
> DCC(Data Capture and Compare) is a DMA engine designed for debugging
> purposes.In case of a system
> crash or manual software triggers by the user the DCC hardware stores
> the value at the register
> addresses which can be used for debugging purposes.The DCC driver
> provides the user with sysfs
> interface to configure the register addresses.The options that the DCC
> hardware provides include
> reading from registers,writing to registers,first reading and then
> writing to registers and looping
> through the values of the same register.
>
> In certain cases a register write needs to be executed for accessing
> the rest of the registers,
> also the user might want to record the changing values of a register
> with time for which he has the
> option to use the loop feature.
>
> The options mentioned above are exposed to the user by sysfs files
> once the driver is probed.The
> details and usage of this sysfs files are documented in
> Documentation/ABI/testing/sysfs-driver-dcc.
>
> As an example let us consider a couple of debug scenarios where DCC
> has been proved to be effective
> for debugging purposes:-
>
> i)TimeStamp Related Issue
>
> On SC7180, there was a coresight timestamp issue where it would
> occasionally be all 0 instead of proper
> timestamp values.
>
> Proper timestamp:
> Idx:3373; ID:10; I_TIMESTAMP : Timestamp.; Updated val =
> 0x13004d8f5b7aa; CC=0x9e
>
> Zero timestamp:
> Idx:3387; ID:10; I_TIMESTAMP : Timestamp.; Updated val = 0x0; CC=0xa2
>
> Now this is a non-fatal issue and doesn't need a system reset, but
> still needs
> to be rootcaused and fixed for those who do care about coresight etm
> traces.
> Since this is a timestamp issue, we would be looking for any timestamp
> related
> clocks and such.
>
> o we get all the clk register details from IP documentation and
> configure it
> via DCC config syfs node. Before that we set the current linked list.
>
> /* Set the current linked list */
> echo 3 > /sys/bus/platform/devices/10a2000.dcc/curr_list
>
> /* Program the linked list with the addresses */
> echo 0x10c004 > /sys/bus/platform/devices/10a2000.dcc/config
> echo 0x10c008 > /sys/bus/platform/devices/10a2000.dcc/config
> echo 0x10c00c > /sys/bus/platform/devices/10a2000.dcc/config
> echo 0x10c010 > /sys/bus/platform/devices/10a2000.dcc/config
> ..... and so on for other timestamp related clk registers
>
> /* Other way of specifying is in "addr len" pair, in below case it
> specifies to capture 4 words starting 0x10C004 */
>
> echo 0x10C004 4 > /sys/bus/platform/devices/10a2000.dcc/config
>
> /* Enable DCC */
> echo 1 > /sys/bus/platform/devices/10a2000.dcc/enable
>
> /* Run the timestamp test for working case */
>
> /* Send SW trigger */
> echo 1 > /sys/bus/platform/devices/10a2000.dcc/trigger
>
> /* Read SRAM */
> cat /dev/dcc_sram > dcc_sram1.bin
>
> /* Run the timestamp test for non-working case */
>
> /* Send SW trigger */
> echo 1 > /sys/bus/platform/devices/10a2000.dcc/trigger
>
> /* Read SRAM */
> cat /dev/dcc_sram > dcc_sram2.bin
>
> Get the parser from [1] and checkout the latest branch.
>
> /* Parse the SRAM bin */
> python dcc_parser.py -s dcc_sram1.bin --v2 -o output/
> python dcc_parser.py -s dcc_sram2.bin --v2 -o output/
>
> Sample parsed output of dcc_sram1.bin:
>
> <hwioDump version="1">
> <timestamp>03/14/21</timestamp>
> <generator>Linux DCC Parser</generator>
> <chip name="None" version="None">
> <register address="0x0010c004" value="0x80000000" />
> <register address="0x0010c008" value="0x00000008" />
> <register address="0x0010c00c" value="0x80004220" />
> <register address="0x0010c010" value="0x80000000" />
> </chip>
> <next_ll_offset>next_ll_offset : 0x1c </next_ll_offset>
> </hwioDump>
>
> ii)NOC register errors
>
> A particular class of registers called NOC which are functional
> registers was reporting
> errors while logging the values.To trace these errors the DCC has been
> used effectively.
> The steps followed were similar to the ones mentioned above.
> In addition to NOC registers a few other dependent registers were
> configured in DCC to
> monitor it's values during a crash. A look at the dependent register
> values revealed that
> the crash was happening due to a secured access to one of these
> dependent registers.
> All these debugging activity and finding the root cause was achieved
> using DCC.
>
> DCC parser is available at the following open source location
>
> https://source.codeaurora.org/quic/la/platform/vendor/qcom-opensource/tools/tree/dcc_parser
>
> Changes in v5:
>
> *Fixed the issue with timeout faced while polling dcc_status register
> in case
> of software triggers.Increased the timeout from 100 us to 5000 us to
> enable
> dcc to process larger register sets in case of software triggers.
>
> Souradeep Chowdhury (4):
> dt-bindings: Added the yaml bindings for DCC
> soc: qcom: dcc:Add driver support for Data Capture and Compare
> unit(DCC)
> MAINTAINERS: Add the entry for DCC(Data Capture and Compare) driver
> support
> arm64: dts: qcom: sm8150: Add Data Capture and Compare(DCC) support
> node
>
> Documentation/ABI/testing/sysfs-driver-dcc | 114 ++
> .../devicetree/bindings/arm/msm/qcom,dcc.yaml | 40 +
> MAINTAINERS | 8 +
> arch/arm64/boot/dts/qcom/sm8150.dtsi | 6 +
> drivers/soc/qcom/Kconfig | 8 +
> drivers/soc/qcom/Makefile | 1 +
> drivers/soc/qcom/dcc.c | 1534
> ++++++++++++++++++++
> 7 files changed, 1711 insertions(+)
> create mode 100644 Documentation/ABI/testing/sysfs-driver-dcc
> create mode 100644
> Documentation/devicetree/bindings/arm/msm/qcom,dcc.yaml
> create mode 100644 drivers/soc/qcom/dcc.c
Gentle Ping
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